Transistor leakage and switching speed may be modulated by a threshold voltage (Vth) of the transistor. Emerging circuits may utilize transistors with multiple threshold voltages to optimize power dissipation and clock frequency. For example, subcircuitry that constrains circuit performance may use lower Vth transistors to increase switching speed and subcircuitry that does not constrain circuit performance may use higher Vth transistors to reduce power consumption. Traditional methods of modulating threshold voltage of a transistor may be based on doping a channel region with different amounts of impurities. For example, an n-type device may have a higher Vth if a greater number of p-type dopants are implanted into the channel. When different transistors are implanted with different levels of channel dopants, different threshold voltages may be realized. However, doping the channel (e.g., by implant) may adversely affect switching speed of a transistor for a given leakage level. Dopant atoms may scatter mobile charge carriers reducing carrier charge mobility. Additionally, transistor performance variation may increase with increasing dopant levels. For example, variation of Vth may increase with increased dopant levels due to random dopant fluctuations.